I don't think we should turn off interactive tile actions during combat. We may want to use them, for example refill a canteen.
The problem I see is the initial if condition. It will always trigger if we have nothing in hand. If the enemy just stole our weapon we can't even punch him in the face for it. So my suggestion would be to change the condition from:
if ( ubCursor == INVALIDCURS || usInHand == NONE )
to:
if ( ubCursor == INVALIDCURS )
This way it would only trigger if we do not have an action selected already.